Polycarbonate cast films of low flammability which consist of 90 to 70% by weight of a high-molecular polycarbonate based on bisphenol A and 10 to 30% by weight of a low-molecular polycarbonate based on halogeno bisphenols are known according to DT-OS (German Published Specification) No. 2,345,533 (Le A 15318)resp. British Pat. No. 1458603. The high molecular polycarbonates based on bisphenol A which have Mw, between about 70,000 and 120,000 are particularly suitable in this situation.
It is known to render thermoplastic aromatic polycarbonates more flame-repellent by adding halogenoalkanesulphonates. (See DT-OS (German Published Specification) No. 1,930,257 (Le A 12 278), DT-OS (German Published Specification) No. 2,253,072 (Le A 14723), U.S. Pat. No. 3,775,367, DT-OS (German Published Specification) No. 2,460,944 and DT-OS (German Published Specification) No. 2,460,787 respectively U.S. Pat. No. 3,931,100).
It is also known to add ammonium salts of perfluoroalkanesulphonic acids to thermoplastic aromatic polycarbonates, as mold release agents for the manufacture of polycarbonate injection-molded articles. (See DT-OS (German Published Specification) No. 2,506,726 (Le A 16 235) and U.S. Pat. No. 4,041,003. However, the use of thermoplastic aromatic polycarbonates containing halogenoalkanesulphonates for the manufacture of films, in particular of extruded films, is not known.